1. Field of the Invention
The present invention relates to power actuated tools for driving fasteners into a substrate and particularly to such tools which operate by detonation of an explosive charge. More particularly the invention relates to power actuated tools in which the fastener such as a nail or pin is fed from a magazine into the tool. The invention also relates to a fastener such as carrier strip for use in such a tool.
2. Description of the Prior Art
Power actuated tools for driving fasteners such as nails or pins into a substrate such as a concrete or steel beam conventionally comprise a barrel from which the fastener is expelled by means of a piston driven by detonation of an explosive charge. Previously proposed tools of this type are described for example in our International patent applications Nos. PCT/AU98/00255 and PCT/AU90/00018 the disclosure of which is hereby incorporated by reference. Tools of the type described in our aforesaid applications are principally designed for use with a single fastener which is loaded manually into the front of the barrel for subsequent discharge when the forward end of the barrel is pressed against the surface to cock the tool to permit firing of the explosive charge upon actuation.
There is now an increasing demand for explosively actuated tools in which the fasteners are loaded automatically or semi-automatically from a magazine. In certain previously proposed tools with magazine feed, the magazine is carried by the body of the tool at the forward end thereof and fasteners are mounted seriatim on successive segments of a carrier strip housed within the magazine. The endmost fastener on the carrier strip is located within an axially displaceable fastener guide which forms an extension of the barrel of the tool, with the tool being cocked for subsequent firing when the forward end of the fastener guide is pressed against the substrate and displaced rearwardly relative to the body of the tool. A practical difficulty with a magazine fed tool is that an operator might not always be aware the supply of fasteners from the magazine has been used and accordingly may be unaware that there is no fastener loaded within the fastener guide. If the tool is fired under these circumstances, the driving piston will be under full power when it strikes an appropriate stop at the forward end of the barrel and which is likely to result in damage to the piston, the barrel, and possibly associated components.